For most Direct Access Storage Devices (DASDs) attached to Multiple Virtual Storage (MVS) systems, data on a volume is described by a Volume Table of Contents (VTOC), and, possibly, by an additional INDEX data set for quicker access to the VTOC data, called data sets. In other words, the VTOC and INDEX data sets show the extents of the volume that are available as free space as well as any extents that currently store data. The VTOC describes the free-space and used-space extents and their locations with different types of Data Set Control Blocks (DSCBs). The INDEX data set is an extension of the VTOC that provides faster access to the data sets and maps out volume free space extents when the VTOC index data set is available.
However, most of the MVS systems are not debugged onsite, as this requires a person with expert knowledge of the system to travel to the remote site in order to examine the error scenario. Therefore, most remote systems are debugged remotely. Currently, if a software error results in corruption of the VTOC or INDEX, problem analysis typically requires an Extended Binary Coded Decimal Interchange Code (EBCDIC) printout of the entire VTOC and INDEX. Often, traces and dumps of the software code that processes the VTOC and INDEX are also requested and obtained. The problem analysis requires a recreation of the error scenario in order to identify the code logic that is in error. Sometimes, it is possible to recreate the error on a smaller-scale, with less data sets than are on the volume; but, again, this requires traces and dumps from the remote system. In other cases, the EBCDIC printout of the VTOC and INDEX are examined and then the information is manually transferred to create a new VTOC and INDEX in the volume for further in-house analysis.
Remote system volumes may contain tens of thousands of data sets or more. Additionally, volume sizes in the future may increase the number of data sets on a volume by several orders of magnitude. As the volume size increases, so does the size of the VTOC and INDEX. Depending on the volume size, and the fragmentation of the data set extents, current debugging processes can become extremely complex and have a number of drawbacks. A first drawback is that debugging of a remote system is a time-consuming, iterative process that requires requests for traces and dumps from the remote system. Another drawback to current debugging techniques is the recreation of the error, which requires visual examination of the EBCDIC printout of the VTOC/INDEX. Another drawback of current techniques is that the processes used may become even more unmanageable if information from the EBCDIC printout needs to be manually transferred to recreate the remote system VTOC/INDEX configuration.
Therefore, a system and method which can recreate remote system error scenarios without requiring visual examination of the EBCDIC printout of the VTOC/INDEX or requests for traces and dumps from the remote system would be very beneficial to the field of debugging remote systems.